Various sensors are known in the magnetic-effect sensing arts. Examples of common magnetic-effect sensors include Hall effect and magnetoresistive technologies. Such magnetic sensors generally respond to a change in the magnetic field as influenced by the presence or absence of a ferromagnetic target object of a designed shape passing through the sensory field of the magnetic-effect sensor. The sensor can then provide an electrical output, which can be further modified as necessary by subsequent electronics to yield sensing and control information. The subsequent electronics may be located either onboard or outboard of the sensor package.
Many of the sensors utilized in automotive applications are configured as position sensors, which provide feedback to a control unit. Many of these types of sensors and related systems are mechanical in nature and are very sensitive to the wearing of contacts, contact contamination, and so forth. To help solve many of the warranty problems associated with mechanical sensors, designers have searched for non-contacting electrical solutions provided by magnetoresistive and/or Hall-effect technologies, which have attempted to detect variance in a magnetic field. One of the primary problems with this approach is the inability of such systems to accurately detect position. The accuracy requirement of such systems makes it difficult, for example, to use a single Hall element because of the offset and shifts over temperature.
The difficulty with both Hall and magnetoresistive technologies is that high accuracy switching points at both low and high RPM's are difficult to achieve. Positions sensors must meet high repeatability requirements for both camshaft and crankshaft applications in automotive devices. In particular, camshaft sensors for newly developed engines require tighter accuracy over all environmental conditions and the ability to determine if the sensor is sensing a target tooth or a target slot as soon as power is applied (i.e., “True Power On” or TPO). Such features allow the engine to be activated sooner and run more efficiently. The present inventor has thus concluded that a need exists for an improved adaptive sensing method and system that can provide high accuracy and highly repeatable switch points through a complete RPM range. The present invention is therefore directed toward improved magnetic sensing methods and systems.